1. Field of the Invention
The field of the invention is directed to hot-fill containers. In particular the field of the invention is directed to ribbed containers.
2. Description of the Related Technology
Plastic containers are used due to their durability and lightweight nature. Polyethylene terephthalate (PET) is used to construct many of today's containers. PET containers are lightweight, inexpensive, recyclable and manufacturable in large quantities.
PET containers are used for products, such as beverages. Often these liquid products, such as juices and isotonics, are placed into the containers while the liquid product is at an elevated temperature, typically between 68° C.-96° C. (155° F.-205° F.) and usually about 85° C. (185° F.). When packaged in this manner, the hot temperature of the liquid is used to sterilize the container at the time of filling. This process is known as hot-filling. The containers that are designed to withstand the process are known as hot-fill containers.
The use of blow molded plastic containers for packaging hot-fill beverages is well known. However, a container that is used in the hot-fill process is subject to additional stresses on the container that can result in the container failing during storage or handling or to be deformed in some manner. The sidewalls of the container can become deformed and/or collapse as the container is being filled with hot fluids. The rigidity of the container can decrease after the hot-fill liquid is introduced into the container. The top-load of a container may also be affected.
After being hot-filled, the hot-filled containers are capped and allowed to reside at about the filling temperature for a predetermined amount of time. The containers and stored liquid may then be cooled so that the containers may be transferred to labeling, packaging and shipping operations. As the liquid stored in the container cools, thermal contraction occurs resulting in a reduction of volume. This results in the volume of liquid stored in the container being reduced. The reduction of liquid within the sealed container results in the creation of a negative pressure or vacuum within the container. If not controlled or otherwise accommodated for, these negative pressures result in deformation of the container which leads to either an aesthetically unacceptable container or one which is unstable. The container must be able to withstand such changes in pressure without failure.
The negative pressure within the container has typically been compensated for by the incorporation of flex panels in the sidewall of the container. Hot-fill containers may typically include substantially rectangular vacuum panels that are designed to collapse inwardly after the container has been filled with hot product. These flex panels are designed so that as the liquid cools, the flex panels will deform and move inwardly. Wall thickness variations, or geometric structures, and the like, can be utilized to prevent unwanted distortion. Generally, the typical hot-fillable container structure is provided with certain pre-defined areas which flex to accommodate volumetric changes and certain other pre-defined areas which remain unchanged.
While the usage of flex panels may be successful, the employment of these flex panels inhibit the usage of different geometries in the formation of the container. Usage of multiple ribs may also be detrimental to the aesthetic appeal of the container. Therefore, there is a need in the field for a container that is able to withstand the hot fill process without utilizing flex panels or multiple ribs, so as to decrease the weight of the container and improve the aesthetic appeal of the container.